These contact members are in the form of spherical domes having a planar base surface, by means of which they are each bonded in a seating disposed for this purpose in each bearing so that the highest point of the domes protrudes from said bearings.
The design of this control element is not entirely satisfactory.
A first disadvantage is that it is difficult to bond the dome-shaped contact members automatically because of the small size of the parts in question (about 2.5 mm). This bonding therefore has to be done manually, thereby increasing production costs.
A second disadvantage is that it is difficult, during bonding to ensure the reproducibility of the distance between the base of the seating which receives the dome and the highest point thereof which makes contact with the ball because it is impossible during manual bonding to deposit a film of adhesive of constant thickness between the base of the dome and the base of the seating. As a result, the ball is poorly positioned and is in danger of rubbing directly against one of the bearings which is not adapted to come into direct contact therewith. This fault leads to premature wear on the ball and, in the longer term, to impaired operation of the control element.
It has moreover been observed that the mere rubbing of the ball against the contact members, even in normal operation, leads to rapid wear on the ball which necessitates its replacement at regular intervals.